CVE-2026-6340

Memory Exhaustion via Malicious 7zip File Upload

State: Published
Severity: 4.3 Medium
Published: May 18, 2026
Updated: May 18, 2026
Reserved: Apr 15, 2026

Description

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate 7zip archive structure before processing which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder declarations.. Mattermost Advisory ID: MMSA-2026-00573

Scores

CVSS	Score	Vector	Source
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L	Mattermost

Weaknesses

CWE-789 Memory Allocation with Excessive Size Value

Affected Products

Product	Versions
MattermostMattermost	11.5.0 through 11.5.1Affected 10.11.0 through 10.11.13Affected 11.4.0 through 11.4.3Affected 11.6.0Not affected 11.5.2Not affected 10.11.14Not affected 11.4.4Not affected

References

MMSA-2026-00573vendor-advisory

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